Can't get tailpiece to seal

[ghopebham]

I just replaced a cracked sink in very tight quarters and cannot get the tailpiece to seal against the sink bottom. I applied silicon sealant to the tapered rubber washer that seats against the sink bottom and am certain that the slip nut is tight, but the leak persists. This sink is mounted on a pedestal (instead of a vanity) and the space between the pedestal, tailpiece, and supply lines is extremely cramped. As a result, the tailpiece and p-trap need to be installed onto the sink before the sink is lowered onto the pedestal, and there’s really no space to tighten the slip nuts for either after the sink is in place. If anyone can offer advice on how to make a reliable seal between the tailpiece and sink bottom, I’ll be grateful.

Greg

 

[breplum]

Are you referring to a 1-1/4 threaded tailpiece or different?
Pictures help.
We have special tools to tighten slip joint nuts, all in place, especially made for pedestal installations. Pasco is the mfr.

 

[ghopebham]

It's a 1-1/4 inch tailpiece.

 

[breplum]

All lav tailpieces are 1-1/4".
Threaded or flat washer seal?

 

[Jeff Handy]

Pictures, pictures, pictures!

If the tailpiece is threaded where it passes through the tapered rubber washer, water can sometimes follow those threads right through the rubber seal.

I always add pipe dope to the threads, then a few wraps of Teflon tape.

 

[TomFOhio]

Is that a plastic pop-up assembly. They are sometimes junk.

 

[ghopebham]

Many thanks to those of you who shared advice. Meanwhile, I watched a few videos and am tackling this again today (Saturday). The space is so tight that a photo would only show the supply valves and part of the p-trap.

After cleaning all the parts, I'll be wrapping the tailpiece threads at the top end and bottom end with teflon tape, applying a bead of plumber's putty around the tapered rubber gasket that seals against the underside of the basin, applying a bead of silicone where the stopper flange seals against the basin drain hole, and probably cursing a bit during "episode two" of this repair.

While the silicone is setting, I'll check back on this thread to see if anyone else has nothing better to do on a Saturday morning! Thank you all!

 

[breplum]

Use plumber's putty on the flange, not silicone.
Use a tiny dab of silicone on underside of basin on threads where the rubber tapered washer comes in contact with the threads that the underside nut uses to cinch up, because water weeps down those threads, even on tapered washers that have ribs to block weeping.
No need for that dab of silicone to set, because it acts as a dam.

 

[ghopebham]

Many thanks to all for suggestions and moral support! The job is finished and although the pros probably already know this, in case anyone reads this thread in the future, stay away from pedestal sinks if you can! The space between a pedestal and the wall is so tight that we even needed to trim the "wings" off the slip nuts and realign the valve knobs to achieve the smidgen more space to tighten everything at the end. Cheers!

 

[Jeff Handy]

Pro tip.
Using 1/4 turn shutoff valves will save space down there, and they have small knobs also.
And a metal p trap will have more compact slip nuts.
But they usually need a wrench to tighten, which can be tough to do, as already pointed out.
Get the heaviest gauge trap, it sucks to have to change it.

 

[breplum]

We only use 17 gauge 1/1/4" ptraps with nuts that are compatible with the Pasco slip joint nut tool (not all nuts have compatible flat sides).